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  2. Nautical mile - Wikipedia

    en.wikipedia.org/wiki/Nautical_mile

    A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. [2] [3] [4] Historically, it was defined as the meridian arc length corresponding to one minute (⁠ 1 / 60 ⁠ of a degree) of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles (that is 60 minutes × 360 degrees).

  3. Light-second - Wikipedia

    en.wikipedia.org/wiki/Light-second

    The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance that light travels in free space in one second, and is equal to exactly 299 792 458 m (approximately 983 571 055 ft or 186 282 mi). Just as the second forms the basis for other units of time, the light-second can ...

  4. Four-minute mile - Wikipedia

    en.wikipedia.org/wiki/Four-minute_mile

    A four-minute mile is the completion of a mile run (1.6 km) in four minutes or less. It translates to a speed of 15 miles per hour (24 km/h). [1] It is a standard of professional middle distance runners in several cultures. The first four-minute mile is usually attributed to the English athlete Roger Bannister, who ran it in 1954 at age 25, in ...

  5. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    For example, in imperial units, the speed of light is approximately 186 282 miles per second, [Note 4] or roughly 1 foot per nanosecond. [ Note 5 ] [ 15 ] [ 16 ] In branches of physics in which c appears often, such as in relativity, it is common to use systems of natural units of measurement or the geometrized unit system where c = 1 .

  6. Foot per second - Wikipedia

    en.wikipedia.org/wiki/Foot_per_second

    km/h. 1.0973. The foot per second (plural feet per second) is a unit of both speed (scalar) and velocity (vector quantity, which includes direction). [1] It expresses the distance in feet (ft) traveled or displaced, divided by the time in seconds (s). [2] The corresponding unit in the International System of Units (SI) is the meter per second.

  7. Light-year - Wikipedia

    en.wikipedia.org/wiki/Light-year

    3.1 × 10 2 ly: Canopus, second in brightness in the terrestrial sky only to Sirius, a type A9 bright giant 10 700 times more luminous than the Sun. 10 3: 3 × 10 3 ly: A0620-00, the second-nearest known black hole, is about 3000 light-years away. 2.6 × 10 4 ly: The centre of the Milky Way is about 26 000 light-years away. [35] [36] 1 × 10 5 ly

  8. Knot (unit) - Wikipedia

    en.wikipedia.org/wiki/Knot_(unit)

    The knot (/ nɒt /) is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h (approximately 1.151 mph or 0.514 m/s). [1][2] The ISO standard symbol for the knot is kn. [3] The same symbol is preferred by the Institute of Electrical and Electronics Engineers (IEEE), while kt is also common, especially in aviation, where it is ...

  9. Ancient Roman units of measurement - Wikipedia

    en.wikipedia.org/wiki/Ancient_Roman_units_of...

    Although the division of hours into minutes and seconds did not occur until the Middle Ages, Classical astrologers had a minuta equal to 1 ⁄ 60 of a day (24 modern minutes), a secunda equal to 1 ⁄ 3600 of a day (24 modern seconds), and a tertia equal to 1 ⁄ 216,000 of a day (0.4 modern seconds).